The present invention relates to a magnetic write/read method of digital information, and more particularly to a magnetic disc apparatus employing constant-density recording and an access method of a magnetic disc driver for accessing data.
The magnetic disc apparatus is capable of storing a large amount of data, providing access to the data at a high rate of speed, and therefore is widely used as an auxiliary memory in computer systems. One type of recording on the magnetic disc apparatus has been based on constant-track-capacity recording. With this type of recording, the magnetic disc apparatus rotates at a constant speed and has the same information capacity per track on both interior and exterior tracks. However, this type of recording has some problems in that the recording density of information on the exterior tracks is rather low, thereby reducing the storage efficiency of the magnetic disc.
In order to solve such a problem, a "constant-density" or a "zone-bit" type of recording has been proposed. The constant-density type of recording is disclosed, for example, in an article "Constant Density Recording Comes Alive With New Chips" by Mark S. Young on pages 141-144 of "Electronic Design" published 13 Nov. 1986. Constant-density recording allows all tracks, including the interior and exterior tracks, to have substantially the same information density so that the information capacity of the magnetic disc can be improved in a system using a small-sized disk driver. In accordance with the constant-density type of recording, the information recording area of the magnetic disc surface is divided into a plurality of zones in which the recording density is constant from the center of the disc to areas extending radially from the center. In the respectively divided track zones, the number of data sectors varies. That is, tracks in the exterior zone have more data sectors than tracks in the interior zone. The data sector indicates a unit area in which the magnetic disc driver accesses data on the magnetic disc surface. Furthermore, the data sector has a uniform size, e.g. 512 bytes, irrespective of its position on the magnetic disc surface. When an embedded servo sector is employed in a servo method, one data sector can be divided into two segments according to the respective zones of the magnetic disc surface. Use of the embedded servo sector is one way to provide location information of the head to the magnetic disc driver. With the embedded servo sector, tracks are respectively divided into a servo information area and a data information area in a circumferential direction about the disc. The servo information area, in which the embedded servo information is recorded, provides the servo sector; and, the data information area, in which real data is recorded, provides the data sector.
As mentioned above, constant-density recording enables all of the tracks to have substantially the same information density, so that a greater amount of data can be recorded on the magnetic disc surface per track, unlike the conventional constant-track-capacity type of recording. Therefore, constant-density recording is widely used in magnetic disc apparatuses.